Removal of textile dyes in wastewater using polyelectrolytes containing tetrazole groups

Biobased hydrogels and their composite containing MgMOF74 for the removal of textile dyes and wastewater treatment

In this work, we report the synthesis of a biobased hydrogel comprised of collagen, chitosan, and polyurethane for the removal of textile dyes. The adsorption capacity of this hydrogel was improved by adding a magnesium metal-organic framework to the semi-interpenetrating polymer matrix yielding a composite hydrogel. Removal of Bismarck Brown and Congo red was studied, and the experimental results fit Freundlich's model. Both hydrogel formulations were tested for the removal of textiles dyes from wastewaters. The magnesium-metal organic framework improved the efficiency of the biobased hydrogel for the removal of direct and mordant dyes reaching up to 89 ± 2%. The composite hydrogel was tested for the removal of Congo Red in a fixed bed column observing the breakthrough point after 168 min. Also, a flocculant material was prepared from collagen and chitosan and was tested for the removal of direct red dye from wastewater removing up to 80 ± 1%. The pretreated wastewater by coagulation-flocculation was treated by adsorption yielding a global removal efficiency of 99%. Finally, the studied hydrogels are potentially biodegradable being completely degraded by the proteolytic action after 22 days. PRACTITIONER POINTS: Composite hydrogels of collagen, chitosan, and MgMOF74 removed efficiently textile dyes from wastewater in batch systems and fixed bed columns. A biobased flocculant of collagen and chitosan significantly improved water quality after coagulation flocculation. Hydrogels were reusable for four cycles, and they can be proteolytically degraded after 22 days.

Synthesis and Characterization of Nanoporous Carbon Carriers for Losartan Potassium Delivery

Losartan potassium is most commonly used for the treatment of hypertension. In recent years, new applications of this drug have emerged, encouraging the design of novel nanoporous carriers for its adsorption and release. The purpose of this study was to synthesize ordered mesoporous carbon vehicles via a soft-templating method altered with the use of nitrogen precursors and via a hard-templating method followed by chitosan functionalization. As a result, the materials obtained differed in nitrogen content as well as in the number of total surface functional groups. The impact of the modification on the physicochemical properties of carbon carriers and their interaction with losartan potassium during adsorption and release processes was examined. The materials were characterized by various morphologies, specific surface areas (101–1180 m² g⁻¹), and the amount of acidic/basic oxygen-containing functional groups (1.26–4.27 mmol g⁻¹). These features, along with pore sizes and volumes, had a key effect on the sorption capacity of carbon carriers towards losartan potassium (59–161 mg g⁻¹). Moreover, they contributed to the differential release of the drug (18.56–90.46%). Losartan potassium adsorption onto the surface of carbonaceous materials was mainly based on the formation of hydrogen bonds and π–π interactions and followed the Langmuir type isotherm. It has been shown that the choice of the method of carbon carriers’ synthesis and their modification allows for the precise control of the kinetics of the losartan potassium release from their surface, resulting in rapid or sustained drug liberation.

Effect of fine structure of chitosan-based flocculants on the flocculation of bentonite and humic acid: Evaluation and modeling

The fine molecular structure of a flocculant fundamentally determines the internal flocculation mechanism and the final application property. In this work, three series of chitosan-based polymers (CTS-g-PAMD) with divergent charge densities and graft chain distribution were synthesized by graft copolymerization using acrylamide (AM) and acryloyloxyethyltrimethylammonium chloride (DAC). Meanwhile, flocculant with linear chain structure (CTS-CTA) was prepared by etherification using 3-chloro-2-hydroxypropyltrimethylammonium chloride (CTA). The characterization results confirmed that various monomers had been successfully introduced into chitosan. The reaction basically happened on -NH₂ at C₂ of chitosan, and the ring structure of chitosan was destroyed by free radical reaction. The obtained flocculants were used to flocculate bentonite and humic acid solution. Besides dose, the effects of chain structure, charge density and chain distribution on flocculation performance were systematically studied. Based on the fractal theory and flocculation kinetics, the effects of structural factors on floc characteristics were also investigated. The results showed that, flocculant with abundant graft chains exerts better flocculation performance and floc characteristic due to enhanced adsorption electrical neutralization and adsorption bridging effect. The effects of charge density and chain distribution on the flocculation performance were disparate in the range of insufficient and excessive doses. Furthermore, on the basis of the quadratic polynomial model, quantitative structure-effect relationships were established, which has guiding significance for the development and utilization of flocculants.